ocean basin

One of two major provinces of the deep ocean
floor, lying over 2 km (1.2 miles) in depth. The mid-ocean
ridges form the other province. Together they constitute 50% of the
Earth's surface. The deep ocean basin is underlain by a basaltic crust,
about 7 km (4.3 miles) thick, and is covered in sediment and dotted by low
abyssal hills. See also ocean
trench.